The human heart generally includes four valves. Of these valves, a most critical one is known as the mitral valve. The mitral valve is located in the left atrial ventricular opening between the left atrium and left ventricle. The mitral valve is intended to prevent regurgitation of blood from the left ventricle into the left atrium when the left ventricle contracts. In preventing blood regurgitation the mitral valve must be able to withstand considerable back pressure as the left ventricle contracts.
The valve cusps of the mitral valve are anchored to muscular wall of the heart by delicate but strong fibrous cords in order to support the cusps during left ventricular contraction. In a healthy mitral valve, the geometry of the mitral valve ensures that the cusps overlie each other to preclude regurgitation of the blood during left ventricular contraction.
The normal functioning of the mitral valve in preventing regurgitation can be impaired by dilated cardiomyopathy caused by disease or certain natural defects. For example, certain diseases may cause dilation of the mitral valve annulus. This can result in deformation of the mitral valve geometry to cause ineffective closure of the mitral valve during left ventricular contraction. Such ineffective closure results in leakage through the mitral valve and regurgitation. Diseases such as bacterial inflammations of the heart or heart failure can cause the aforementioned distortion or dilation of the mitral valve annulus. Needless to say, mitral valve regurgitation must not go uncorrected.
One method of repairing a mitral valve having impaired function is to completely replace the valve. This method has been found to be particularly suitable for replacing a mitral valve when one of the cusps has been severely damaged or deformed. While the replacement of the entire valve eliminates the immediate problem associated with a dilated mitral valve annulus, presently available prosthetic heart valves do not possess the same durability as natural heart valves.
Various other surgical procedures have been developed to correct the deformation of the mitral valve annulus and thus retain the intact natural heart valve function. These surgical techniques involve repairing the shape of the dilated or deformed valve annulus. Such techniques, generally known as annuloplasty, require surgically restricting the valve annulus to minimize dilation. Here, a prosthesis is typically sutured about the base of the valve leaflets to reshape the valve annulus and restrict the movement of the valve annulus during the opening and closing of the mitral valve.
Many different types of prostheses have been developed for use in such surgery. In general, prostheses are annular or partially annular shaped members which fit about the base of the valve annulus. The annular or partially annular shaped members may be formed from a rigid material, such as a metal, or from a flexible material.
While the prior art methods mentioned above have been able to achieve some success in treating mitral regurgitation, they have not been without problems and potential adverse consequences. For example, these procedures require open heart surgery. Such procedures are expensive, are extremely invasive requiring considerable recovery time, and pose the concomitant mortality risks associated with such procedures. Moreover, such open heart procedures are particularly stressful on patients with a compromised cardiac condition. Given these factors, such procedures are often reserved as a last resort and hence are employed late in the mitral regurgitation progression. Further, the effectiveness of such procedures is difficult to assess during the procedure and may not be known until a much later time. Hence, the ability to make adjustments to or changes in the prostheses to obtain optimum-effectiveness is extremely limited. Later corrections, if made at all, require still another open heart surgery.
An improved therapy to treat mitral regurgitation without resorting to open heart surgery has recently been proposed. This is rendered possible by the realization that the coronary sinus of a heart is near to and at least partially encircles the mitral valve annulus and then extends into a venous system including the great cardiac vein. As used herein, the term “coronary sinus” is meant to refer to not only the coronary sinus itself but in addition, the venous system associated with the coronary sinus including the great cardiac vein. The therapy contemplates the use of a device introduced into the coronary sinus to reshape and advantageously effect the geometry of the mitral valve annulus.
The device includes a resilient member having a cross sectional dimension for being received within the coronary sinus of the heart and a longitudinal dimension having an unstressed arched configuration when placed in the coronary sinus. The device partially encircles and exerts an inward pressure on the mitral valve. The inward pressure constricts the mitral valve annulus, or at least a portion of it, to essentially restore the mitral valve geometry. This promotes effective valve sealing action and eliminates mitral regurgitation.
The device may be implanted in the coronary sinus using only percutaneous techniques similar to the techniques used to implant cardiac leads such as pacemaker leads. One proposed system for implanting the device includes an elongated introducer configured for being releasably coupled to the device. The introducer is preferably flexible to permit it to advance the device into the heart and into the coronary sinus through the coronary sinus ostium. To promote guidance, an elongated sheath is first advanced into the coronary sinus. Then, the device and introducer are moved through a lumen of the sheath until the device is in position within the coronary sinus. Because the device is formed of resilient material, it conforms to the curvatures of the lumen as it is advanced through the sheath. The sheath is then partially retracted to permit the device to assume its unstressed arched configuration. Once the device is properly positioned, the introducer is then decoupled from the device and retracted through the sheath. The procedure is then completed by the retraction of the sheath. As a result, the device is left within the coronary sinus to exert the inward pressure on the mitral valve to restore mitral valve geometry.
The foregoing therapy has many advantages over the traditional open heart surgery approach. Since the device, system and method may be employed in a comparatively noninvasive procedure, mitral valve regurgitation may be treated at an early stage in the mitral regurgitation progression. Further, the device may be placed with relative ease by any minimally invasive cardiologist. Still further, since the heart remains completely intact throughout the procedure, the effectiveness of the procedure may be readily determined. Moreover, should adjustments be deemed desirable, such adjustments may be made during the procedure and before the patient is sent to recovery.
Another approach to treat mitral regurgitation with a device in the coronary sinus is based upon the observation that the application of a localized force against a discrete portion of the mitral valve annulus can terminate mitral regurgitation. This suggests that mitral regurgitation may be localized and nonuniform. Hence, the device applies a force to one or more discrete portions of the atrial wall of the coronary sinus to provide localized mitral valve annulus reshaping instead of generalized reshaping of the mitral valve annulus. Such localized therapy would have all the benefits of the generalized therapy. In addition, a localized therapy device may be easier to implant and adjust.
A still further approach to treat mitral regurgitation from the coronary sinus of the heart contemplates a device having a first anchor configured to be positioned within and fixed to the coronary sinus of the heart adjacent the mitral valve annulus within the heart, a cable fixed to the first anchor and extending proximally from the first anchor within the heart, a second anchor configured to be positioned in and fixed in the heart proximal to the first anchor and arranged to slidingly receive the cable, and a lock that locks the cable on the second anchor. When the first and second anchors are fixed within the heart, the cable may be drawn proximally and locked on the second anchor. The geometry of the mitral valve is thereby effected. This approach provides flexibility in that the second anchor may be positioned and fixed in the coronary sinus or alternatively, the second anchor may be positioned and fixed in the right atrium. This approach further allows adjustments in the cable tension after implant.
A still further alternative for treating mitral regurgitation contemplates a device having a first anchor configured to be positioned within and anchored to the coronary sinus of the heart adjacent the mitral valve annulus within the heart. A second anchor is configured to be positioned within the heart proximal to the first anchor and adjacent the mitral valve annulus within the heart. A connecting member, having a fixed length, is permanently attached to the first and second anchors. As a result, when the first and second anchors are within the heart with the first anchor anchored in the coronary sinus, the second anchor may be displaced proximally to effect the geometry of the mitral valve annulus and released to maintain the effect on the mitral valve geometry. The second anchor may be configured, when deployed, to anchor against distal movement but be movable proximally to permit the second anchor to be displaced proximally within the coronary sinus.
A further device that effects the condition of a mitral valve annulus of a heart also includes an elongated member dimensioned to be placed in the coronary sinus of the heart adjacent the mitral valve annulus. Here, the elongated member is flexible when placed in the heart in a first orientation to position the device in the coronary sinus adjacent the mitral valve annulus and relatively inflexible when rotated into a second orientation after the device is positioned in the coronary sinus adjacent to the mitral valve annulus.
The device thus has a first radius of curvature when in the first orientation and a second and greater radius of curvature when in the second orientation to effect the mitral valve geometry. Once positioned and in the second orientation, the device is anchored against both longitudinal and rotational movement.
Devices, other than those described above may be placed in body lumens other than the coronary sinus for therapeutic effect. All such devices must be anchored against movement when deployed at least for an acute phase until the natural body mechanisms produce sufficient fibrotic tissue about the devices for permanent fixation. While the device anchors must protect against device movement, they must also allow ready deployment to facilitate device implant. However, it is desirable that the anchors also be readily releasable, at least during the acute phase to permit device position adjustment or even device removal if required. All of these factors are especially important for devices implanted in the heart because of the potential need for precise device positioning during implant and the extreme movement of the heart during heartbeats.